Format a String in IPhone - iphone

Question

I need to add space after every 4 characters in a string.. For example if the string is aaaaaaaa, i need to format it as aaaa aaaa. I tried the following code, but it doesn't work for me.
NSMutableString *currentFormattedString = [[NSMutableString alloc] initWithString:formattedString];
int count = [formattedString length];
for (int i = 0; i<count; i++) {
if ( i %4 == 0) {
[currentFormattedString insertString:#" " atIndex:i];
}
}
Can anyone help me with this?

Answer 1

You haven't said what isn't working with your code, so it's hard to know exactly what to answer. As a tip - in future questions don't just say "it isn't working", but state WHAT isn't working and HOW it isn't working. However...
NSMutableString *currentFormattedString = [[NSMutableString alloc] initWithString:formattedString];
int count = [formattedString length];
for (int i = 0; i<count; i++) {
if ( i %4 == 0) {
[currentFormattedString insertString:#" " atIndex:i];
}
}
You are inserting a space, but you are not then accounting for this in your index value. So, suppose your formattedString is aaaaaaaaaaaaaaaa
The first time through your loop, you will get to the 4th position and insert a space at i=4
aaaa aaaaaaaaaaaa
Now the next time you get to insert a space, i will be 8. But the 8th position in your currentFormattedString isn't where you think it will be
aaaa aaa aaaaaaaaa
Next time it will be another 4 characters along which still isn't where you think
aaaa aaa aa aaaaaaa
And so on
You have to take into account the inserted space which will affect the offset value.

Answer 2

NSString *text = [[NSString alloc] initWithString:#"aaaaaaaa"];
NSString *result = [[NSString alloc] init];
double count = text.length/4;
if (count>1) {
for (int i = 0; i<count; i++) {
result = [NSString stringWithFormat:#"%#%# ",result,[text substringWithRange:NSMakeRange(i*4, 4)]];
}
result = [NSString stringWithFormat:#"%#%# ",result,[text substringWithRange:NSMakeRange(((int)count)*4, text.length-((int)count)*4)]];
}
else result = text;

Answer 3

I found the following which formats a string to a telephone number format, but it looks like you could easily change it to support other formats
Telephone number string formatting

Answer 4

Nick Bull answered on the reasons why your method broke already.
IMHO the appropriate solution would be to use a while loop and do the loop increments yourself.
NSInteger i = 4; // first #" " should be inserted after the 4th (index = 3) char
while (i < count) {
[currentFormattedString insertString:#" " atIndex:i];
count ++; // you did insert #" " so the length of the string increased
i += 5; // you now must skip 5 (" 1234") characters
}